D-MOTION is a feature that changes the tone parameter you set according to how you tilt the SH-4d (both forward/backward and left/right). With the modulation matrix, you can use D-MOTION to affect other parameters by setting the parameter (MOD or AFT) to which the D-MOTION effect is applied as its modulation source.
For details on how to do this, refer to “Using D-MOTION” in “SH-4d Reference Manual”.